Lasers for treating skin ailments, hair removal, and other dermal procedures were first introduced in the 1990s. Laser wavelengths are absorbed in the skin or in other tissues to provide limited localized damage, which causes the body to respond in a desired manner. One example includes lasers that provide localized damage to hair follicle cells, which causes permanent hair removal. Another example includes lasers that provide localized damage to the dermal layers, which causes wrinkle or acne reduction in the skin.
A schematic drawing of the outer layers of the skin is shown in FIG. 5. The outer layer of the skin, the epidermis, is the familiar outer layer of skin cells. Below the epidermis is the dermis, which comprises living epidermal cells, local vascularization, and additional structures including hair follicles, collagen, elastin and secretory cells. The dermis is the primary target site for treatment of the skin for lasting or permanent changes. It is most desirable to leave the epidermis unaffected and undamaged during a treatment procedure. To achieve this, the epidermis can be intentionally cooled during such treatment procedure, or the procedure can be tailored to avoid any significant heat to the epidermis. This approach will minimize pain and recovery times and ideally with no visible scarring, redness, or side effects.
There are a number of past and current examples of laser treatments for skin. For example, U.S. Pat. No. 8,029,553 to Nemenov describes a laser system and process using a near-IR laser at 980 nanometers (nm) to produce controlled variable heating and stimulation of single nerve fibers in tissue, while avoiding nerve damage. U.S. Pat. No. 7,856,985 to Mirkov et al. and U.S. Published Patent Application No. 2011/0152847 by Mirkov et al. describe remodeling of skin using high intensity laser pulses to shrink skin collagen, and using low intensity radiation to stimulate fibroblasts for renewed collagen production. U.S. Pat. No. 7,413,572 to Eimerl et al. describes irradiating tissue with a sequence of optical pulses. Then, tissue properties are measured and used to vary the intensity of irradiation to produce desired results. U.S. Pat. No. 6,998,567 to Yeik describes the creation and delivery of laser pulse trains.
U.S. Pat. No. 6,595,985 to Tobinick uses laser pulses to remove hair follicles and cooling the epidermis with fluid spray to prevent skin damage. U.S. Pat. Nos. 6,165,171 and 6,168,589 to Tobinick describe two lasers of different wavelengths to remove hair follicles. U.S. Pat. No. 5,836,999 to Eckhouse et al. discloses treatment of psoriasis with non-laser optical energy. In this example, pulse number and width are selected to control penetration, and cooling may be supplied to the skin surface. U.S. Pat. No. 5,689,520 to Hoang describes a method and apparatus for obtaining a variable output waveform in surgery.
U.S. Pat. No. 5,269,778 to Rink et al. and U.S. Pat. No. 4,950,268 to Rink use pulses for vaporization of tissue at a tissue site producing localized plasma.